Veterinary Research Forum

Abstract The accessory gene regulator(agr) operon as a part of the quorum-sensing (QS) system, is responsible for the regulation of numerous virulence factors in Staphylococci. Furthermore, the ability of the opportunistic pathogen, Staphylococcus pseudintermedius to form biofilm is a significant contributor to chronic diseases. Our aim was evaluation of the association between different agr groups and the expression of icaD gene related to biofilm formation among S. pseudintermedius from nasal samples. Fifty nasal swabs were collected from broiler chickens; then phenotypic and molecular tests performed for isolation of S. pseudintermedius from samples and their agr genotype was also investigated. The biofilm production capacity of the isolates was determined using both microtiter plate assay and amplification of icaD gene. S. pseudintermedius was detected in 86.84% of samples. The assessment of agr typing results related that most of the strains (69.70%) were classified in agr group ɪ. The relative frequency of biofilm producing S. pseudintermedius isolates was 75.76% and all of them harbored icaD gene. The expression level of icaD determinant was significantly higher among isolates in agr group ɪ than other agr groups. The results suggest that broiler chickens may act as a reservoir for transmission of S. pseudintermedius to humans which should be considered a potential zoonotic bacterium able to produce different virulence factors like biofilm.

Abstract This study aimed to evaluate the effects of different copper sources experimental copper sulfate (CS), copper methionine (CM), copper carbohydrate (CC), copper dihydrogen phosphate (CP), and Nano copper (CN) on growth performance, carcass characteristics, and intestinal histomorphology in broiler chickens. A total of 300 day-old broilers were randomly assigned to five dietary treatments with six replicates each. During the finisher and the whole experimental periods, CM- and CN-fed birds had the highest and lowest body weight gain, respectively, as compared to the birds in other treatments. Consumption of the CM diet increased the feed intake compared to the different treatments. Feed conversion ratio was increased by consumption of CN as compared to CM during the finisher and the whole experimental periods. In the duodenum, villus height (VH) was significantly increased by CN as compared to control. In the jejunum, consumption of both the CM and CC diets caused the lowest VH, whereas dietary CN inclusion resulted in the highest VH. The VH/crypt depth (CD) ratio was at the lowest and highest levels by CM and CN, respectively. In the ileum, villus width was numerically decreased by CP. CS-fed birds had the highest CD between the treatments. The VH/CD ratio was higher in CP and CN-fed birds as compared to CS ones. Moreover, the goblet cell number was decreased by dietary CP as compared to CM. In conclusion, broiler performance was increased by both CM and CP sources of copper, with methionine-based copper being suggested as a component of chicken diets.

Abstract The aims of current investigation were to study the growth performance, carcass traits, meat quality and expression profile of Myostatin (MSTN), Insulin-like growth factor-1 (IGF-I), Myogenin (MyoG) and Myogenic regulatory factor 4 (MRF4) genes in three commercial broiler strains including Ross (Ross 308), Cobb (Cobb 500), and Arian in 2023. A total number of 240 one-day-old chicks were reared under an equalized standard management condition for 6 weeks. Performance, organ weights, meat quality and the expression level of the myogenic genes in the pectoral muscle were investigated. The lowest body weight (BW), feed intake, weight gain and highest feed conversion ratio (FCR) was observed for Arian at the end of the study. The meat quality was similar between strains. The IGF-I expression level was significantly higher on 42 days of age in Cobb compared to Ross and Arian. The MRF4 expression level was significantly higher on 28 days of age in Cobb compared to Ross. The MyoG expression level was significantly lower in Arian compared to Cobb on 42 days of age. Furthermore, the MSTN expression level was significantly lower in Cobb compared to Ross and Arian on 42 days of age. The remarkable differences in gene expression levels at the end of the rearing period was supported by higher growth performance and BW of Cobb compared to Ross and Arian strains. In conclusion, the findings of current study could conveniently help assess the performance of these broiler strains under similar rearing condition.

Abstract The developmental morphology of the bursa of Fabricius (BF) of broiler chicken was evaluated in this study using gross anatomical, histological, reticulin histo-chemical, and transmission electron microscopic techniques. The result showed that the short plica of the BF at embryonic day (ED) 14 was a mesenchymal tissue that contained cells, including mesenchymal cells and lymphoblasts. The organo-somatic index (OSI) of the BF peaked at ED 17, while the BF of ED 19 showed well delineated follicle-associated and inter-follicular epithelial (IFE) cells. Whereas, the IFE contained apical vacuoles which increased in size with age, the BF contained lymphoid follicles which were first observed at ED 17, and increased steadily in mean diameter from ED 19 to post-hatch day (PD) 28. The framework of the inter-follicular areas and the follicular capsules were composed of collagen type III fibres. Moreover, the cortico-medullary basement membranes were well established with peripheral and cortico-medullary basement capillaries becoming very consistent between PDs 5 and 7. The lymphoid follicle contained lymphocytes with mitotic figures, and plasma cells which showed extensive network of rough endoplasmic reticulum at PD 21, while macrophages contained increasing evidence of phagocytosis from PDs 35 to 56. In conclusion, the morphological features of the BF of broiler chicken in this study reveals that the key function of B-cell maturation within the BF may occur between the first 3 to 4 weeks after hatching, and thereafter, may primarily produce immunoglobulins until involution occurs.

Abstract Spondylolisthesis known as kinky back syndrome is a deformity of the free sixth thoracic vertebra including enlargement and rotation resulting in posterior paralysis in broiler chicken. Genotype, feeding regimes and environment are involved in occurrence of this congenital anomaly. Spondylolisthesis may result in or happen simultaneously with two other major axial skeleton pathologies including spondylosis and spondylitis as a result of occurrence of degenerative necrobiotic lesions and inflammation of the vertebrae, respectively. This report deals with a male broiler chicken with posterior paralysis in the second week of rearing. After euthanasia, the specimen was evaluated at macroscopic and microscopic levels. Macroscopic findings showed the unilateral enlargement of body and transverse process of sixth thoracic vertebra and downward rotation of the body. The histopathological studies revealed the focal chondronecrosis and degenerative changes in articular facets and cranial process of the vertebra. In conclusion, a diagnosis of spondylolisthesis followed by spondylosis was made based on macroscopic and histopathological findings that to the authors’ best knowledge, is the first report in a broiler farm in Iran.

Abstract The effect of Shirazi thyme as a medicinal plant on oxidant status (lipid peroxidation, protein oxidation, total antioxidant capacity and catalase activity) and absorptive surface area were measured in three segments of small intestine in cold-induced pulmonary hypertensive chickens. Birds were reared at 4 groups (thyme 0, 0.25, 0.5 and 1 % of diet) for 42 days. To induce pulmonary hypertension, the temperature was gradually decreased. The body weight was increased in thyme-0.25% birds in compared to control ones while it was decreased in thyme-1% birds. The feed consumption was only increased in thyme-1% birds. The feed conversion ratio was lower in thyme-0.25% birds and higher in thyme-1% birds than control ones. The duodenal and jejunal villus surface area was lower in thyme-1% birds than control ones while it was greater in the thyme-0.5% birds. The ileal villus surface area and duodenal laminae properia thickness was also greater in thyme-0.5% birds. Lipid peroxidation was only decreased in the duodenum and ileum of thyme-0.5% birds compared to control ones, whereas it was increased in the duodenum and jejunum of thyme-1% birds. Catalase activity was only elevated in the duodenum and jejunum of thyme-1% fed chickens. Total antioxidant capacity was increased in the duodenum, jejunum and ileum of thyme-0.5% birds. It is concluded that Shirazi thyme has beneficial effects on growth performance, intestinal absorptive surface area / secretory system and pulmonary hypertension response at low doses (0.25 and 0.5% fed) whereas high dose of this plant may be toxic (1% fed).

Abstract Excessive consumption of red meat is associated with various diseases including coronary heart diseases and cancer. Lower health-related problems of chicken meat, consumption of chicken meat, and mechanically deboned chicken meat (MDCM) have been increased due to their cheaper prices. Thereby, chemical, microbial, and physical causes of chicken meat losses and the safety aspects are needed to be fully considered to save food by improved application of chicken meat and its by-product. This study investigated the effects of chicken classes, layer, and broiler, and different carcass cuts, fillet, skeleton, and the whole carcass, on physicochemical, protein, fat, ash, moisture, pH, and peroxide, and microbiological, total plate counts, Escherichia coli, Staphylococcus aureus, Campylobacter, and Salmonella, characteristics as well as introducing content changes of metal elements iron, calcium (Ca), lead, cadmium, and arsenic in MDCM. The highest values of physicochemical characteristics, calcium, iron, and heavy metals were observed in deboned layer chicken carcass and deboned broiler skeleton (p<0.05). Although Escherichia coli was detected in all of the treatments, Salmonella, Staphylococcus aureus, and Campylobacter contamination were found only in the deboned layer and broiler skeleton. In conclusion, the application of MDCM by-products in meat products without thermal processing is not recommended. The broiler and layer skeleton MDCMs are not suitable for human consumption due to the high contents of heavy metals. However, the whole carcasses of layer chickens are suitable to be mutually used in MDCM at the end of the egg laying period.

Abstract The efficacy of probiotics as alternatives to antibiotics has been defined as one of the potential strategies to prevent Salmonella spp. infection in poultry. The purpose of this study was to isolate probiotic native Lactic acid bacteria (LAB) with high compatibility to intestinal tract and prevention of Salmonella typhimuriumfrom broiler chicken feces. Thirty-seven samples of chicken feces were collected from seven broiler chicken farms in Northern Iran. The isolates identification was carried out with morphological and biochemical tests. Agar diffusion methods were used to evaluate the antimicrobial activities against Escherichia coli and S. typhimurium. The primary probiotic characteristics such as resistance to acid and bile and adhesion to Caco-2 cells were studied. Indeed, the ability of LAB isolates to inhibit adhesion of S. typhimurium to Caco-2 cells was evaluated by exclusion, competition and displacement assays. Among 42 isolates, S08, S01 and S06 isolates which showed appropriate probiotics characteristics were selected. Isolates S08 and S01 showed to be able to adhere strongly and also S06 was adhered moderately. In the exclusion assay, the isolates S08, S01 and S06 significantly hampered adhesion of S. typhimurium cell, in the competition assay, the isolates S08, S01 showed significant level of competition activity against S. typhimurium adherence to Caco-2 cells and isolate S08 showed the greatest displacement activity. The 16S rDNA sequence revealed that S08, S01, and S06 isolates were 99.00% similar to Lactobacillus salivarius, Lactobacillus johnsonii, and Pediococcus acidilactici, respectively. The result of this study suggested that LAB isolated from broiler chicken feces could be a remarkable reservoir for identification of probiotic to inhibit the pathogenic bacteria growth.

Abstract Characterization of isolated pigeon paramyxovirus-1 (PMV-1) and its pathogenicity in broiler chickens were studied. Two hundred and thirty-two samples collected from 50 unvaccinated pigeons lofts suspected to Newcastle disease from private houses and bird markets from Ahvaz‌, Iran. Swab samples from cloaca and oropharynx of live pigeons and from trachea, lung, liver, spleen, kidney, brain, proventriculus and cecal tonsil of dead pigeons suspected to ND were collected. Isolation of the PPMV-1 was performed through intra-allantoic inoculation of 9- to 11- day-old embryonated chicken eggs. The RNA extraction and cDNA synthesis were conducted. With PCR, multiplication of cleavage site of F gene was carreid out and PCR products were sequenced and phylogenetic comparison on isolates was performed. For pathogenecity study of isolated PPMV-1, one hundred sixty day-old broiler chicks were divided into four equal groups. Groups 1 and 2 chicks vaccinated against ND by B1 vaccine at nine days. Groups 3 and 4 were kept as unvaccinated control groups. Groups 1 and 4 chicks were challenged with 10⁵EID₅₀ of highest virulent isolated PPMV-1 by ocular route at day 29. The results indicated PPMV-1 is enzootic in Ahvaz pigeons and all isolates were virulent Newcastle disease virus with 112KRQKR*F117 motif. For study pathogenicity of pigeon isolate in chickens, they challenged with most virulent isolate, showed respiratory signs, conjunctivitis and in some cases depression and lethargy. In conclusion, isolated PPMV-1 is a virulent NDV and can infect chickens and produce mild ND in unvaccinated chickens.

Abstract Ornithobacterium rhinotracheale (ORT) is a bacterium associated with respiratory disease, growth retardation, decreased egg production and mortality in chickens and turkeys. The objective of this study was isolation, identification and evaluation of antimicrobial susceptibility of ORT bacterium in slaughtered broilers chicken flocks based on cultural and molecular tests in Khuzestan province, south-west of Iran. A total of 210 tracheal swab samples were collected from 21 broiler flocks slaughtered in abattoirs of the province. The results of cultural and biochemical tests showed that 23 (10.95%) isolates from tracheal swabs of 4 flocks (19.04%) were identified as ORT, but according to molecular characterization, 18 (8.57%) ORT isolates were positive in PCR assay and produced the predicted 784 bp amplification product. Finally, using the disk diffusion method, the drug resistance patterns of ORT isolates were determined against a panel of commonly used antimicrobial agents. Antimicrobial susceptibility test revealed that all isolates (100%) were sensitive to tetracycline, florfenicol and cephalexin. The highest antimicrobial resistance (89.00%) was seen for fosfomycin, sultrim and gentamicin. The results of present research showed that there was significant difference between the isolation rates of ORT from various areas of the province. As well, our findings indicated that the simultaneous use of both cultural and molecular techniques results in more comprehensive outcomes in the isolation and identification of the organismfrom understudy hosts.

Abstract The present experiment was conducted to evaluate the effects of organic acids and phytase enzyme supplementation on performance and intestinal histomorphology of broilers. The experiment was done in a factorial arrangement 2 × 2 × 2 based on completely randomized design with eight treatments, five replicates with 12 chicks in each until 42 days of age. Diets included natural vinegar (0 and 2%), citric acid (CA; 0.00 and 1.00%) and phytase enzyme (PHY; 0.00 and 500 FTU phytase per kg of feed). One bird from each treatment replicate was randomly selected and slaughtered to evaluate the small intestinal morphology on 42 days of age. Analysis of results showed that vinegar increased feed consumption and body weight gain in total experimental period (p ˂ 0.05), while CA significantly decreased feed consumption on 0-14 days of age (p ˂ 0.05). No effect was observed on performance in interaction of organic acids together and with PHY group (p > 0.05). In duodenum CA increased the villusheight and width (p ˂ 0.05) and PHY enzyme increased villuswidth (p ˂ 0.05) and decreased crypt depth (p ˂ 0.05). On the other hand, CA along with PHY significantly decreased crypt depth (p ˂ 0.05). In jejunum PHY alone and in combination with vinegar increased the goblet cells numbers (p ˂ 0.05), whereas vinegar significantly increased the goblet cells numbers in ileum (p ˂ 0.05). The muscular thickness in duodenum, jejunum, and ileum was not affected among different treatment groups. The results showed that supplementation of organic acids and phytase together in this experiment, with no negative effects on each other, improved their effects on some parameters.

Abstract The objective of this study was to investigate development of the weight and the morphological development of the rectum in broiler chickens. Twenty broiler chickens (Ross 308) were used in this experiment and they were 12, 20, 35 and 44 days of age. Samples from the rectum of chicks were sectioned in an unbiased manner and examined quantitatively using stereology. In addition, the weight of both body (BW) and rectum and also rectum weight as a proportion of BW, height and width of the villi and thickness of rectum wall were measured. The results revealed that the body and rectum weight were increased with age. The greatest rectum weight as a proportion of BW was observed on day 20. An increase in height and width of the villi during the study period were obtained. The increase was more significant on days 35 and 44 than on days 12 and 20 (p < 0.05). There were significant difference in thickness of tunica mucosa, submucosa and muscular layer of the rectum on day 20 compared to day 35 (p < 0.05). The increase in the volume density of the wall, tunica mucosa and tunica muscular was greater on day 20 than on day 35. However, significant differences were observed in volume density of this layers between days 35 and 44 compared to days 12 and 20 (p < 0.05).

Abstract The effects of dietary vitamin E levels on mucosal maltase and alkaline phosphatase (ALP) enzyme activities and on the amount of mucosal malonyldialdehyde (MDA) in broiler chickens were studied in the present study. One hundred and eighty of day old male broiler chicks (Ross 308 strain) were randomly assigned into five groups, each with three replicates and 12 chicks in each replicate. Chickens in group A were fed corn-soy- based diet, while those in groups B, C, D and E were fed the same diet with 20, 60, 180, and 540 mg kg^-1 vitamin E supplement (d-alpha tocopherol), respectively. Six birds were randomly chosen from each group, and were euthanized on days 10, 21, 32, and 42 of age. One segment of small intestine outset was homo-genized and mucosal ALP and maltase activity were measured. Moreover, mucosal lipid peroxidate amount was measured to reveal the impact of vitamin E on oxidative stress. Maltase activity was increased with the increase of vitamin E up to 60 mg kg^-1 of diet while with further levels, it was decreased. Addition of 60 mg kg^-1 of vitamin E to the diet significantly increased ALP enzyme activity (p ≤ 0.001). Addition of 540 mg kg^-1 of vitamin E supplement to the diet led to the minimum amount of MDA at 32 days of age. It may be concluded that supplementation of broiler's diet with 60 mg kg^-1of vitamin E can increase mucosal maltase and ALP enzyme activity.

Abstract This experiment was conducted to compare the effects of prebiotic as alternative feed additive to an antibiotic growth promoter (bacitracin methylene disalicyate) on the growth performance and morphometrical parameters of the small intestine of broiler chickens. One hundred and forty four day old broiler chicks were randomly assigned to one of three dietary treatments for 6 wk and each treatment contained four replicates (12 birds each). Dietary treatments were as follow: 1- Control (basal diet), 2- basal diet + antibiotic growth promoter and 3- basal diet + prebiotic. During the feeding experimental period, body weight, weight gain, feed intake and feed conversion ratio were measured. At the end of the experiment, small intestine segments were sampled and routine histological laboratory methods containing fixation, dehydration, clearing and paraffin embedding were used. Sections stained with haematoxylin and eosin for light microscopy evaluation and the height and width of villi and depth of crypts were measured. The results showed that body weight, weight gain and feed conversion ratio were not affected by dietary treatments. Prebiotic and antibiotic had significant (P < 0.05) effect on improvement of feed intake in 22 - 42 days and total period compared with the control. The addition of prebiotic or antibiotic increased the villus height in duodenum (P < 0.05) and prebiotic increased villus width of duodenum and ileum compared with other treatments. The duodenal crypt depth was increased by antibiotic compared with the prebiotic and control group. In conclusion, prebiotic can be used as a suitable alternative to antibiotic growth promoter.